A halogen-containing corrosive gas atmosphere prevails in most semiconductor manufacturing apparatus, and flat panel display manufacturing apparatus such as liquid crystal, organic EL and inorganic EL manufacturing apparatus. Apparatus components are made of high purity materials in order to prevent workpieces from impurity contamination.
The semiconductor manufacturing process employs gate etching systems, insulating film etching systems, resist film ashing systems, sputtering systems, CVD systems and the like. On the other hand, the liquid crystal manufacturing process employs etching systems for forming thin-film transistors and the like. In these processing systems, a plasma-producing mechanism is incorporated for microprocessing to a high degree of integration.
In these processing steps, corrosive gases containing halogen (e.g., fluorine or chlorine) are used as the processing gas due to their reactivity. Typical fluorine-containing gases include SF6, CF4, CHF3, ClF3, HF, NF3, etc. Typical chlorine-containing gases include Cl2, BCl3, HCl, CCl4, SiCl4, etc. When microwave or high frequency is applied to an atmosphere into which such gases have been fed, the gases are activated to a plasma. System members which are exposed to such halogen-containing gases or plasma thereof are required to be highly corrosion resistant.
In view of the above requirement, the materials used in the art to impart corrosion resistance to halogen-containing gas or plasma thereof include ceramics such as quartz, alumina, silicon nitride, and aluminum nitride, anodized aluminum (alumite) coatings, and substrates having coatings of the foregoing ceramics thermally sprayed on their surface. JP-A 2002-241971 discloses a plasma-resistant member comprising a surface region to be exposed to a plasma in a corrosive gas atmosphere, the surface region being formed of a Group IIIA metal layer. The layer has a thickness of about 50 to 200 μm.
However, the ceramic members suffer from the problems that the working cost is high and particles are left on the surface. When the ceramic members are exposed to a plasma in a corrosive gas atmosphere, corrosion proceeds gradually, though to a varying extent depending on the identity of ceramic material. As a result, crystal grains lying in the surface region spall off, causing the so-called “particle contamination.” Once spalling off, the particles deposit in proximity to the semiconductor wafer, lower electrode or the like, adversely affecting the etching precision and the like and detracting from the performance and reliability of the semiconductor.
Since the reaction products deposited on the member surface cause particle contamination, the reaction products must be removed by washing. The washing step often uses water. However, the reaction products can react with water to produce acids, which have detrimental impact on the plasma-resistant coating layer and substrate, substantially altering the life of the member.
As the current semiconductor technology is stepping forward targeting a finer feature size and a larger wafer diameter, the so-called dry process, especially etching process, has started using a low-pressure high-density plasma. As compared with conventional etching conditions, the low-pressure high-density plasma has significant impact on plasma-resistant members, giving rise to outstanding problems including erosion by the plasma, contamination of the members caused by the erosion, and contamination with reaction products of surface impurities.